Under normal conditions, the thyroid takes in iodine ion 120μg from the extracellular liquid iodine pool every day, of which 60μg is used to synthesize thyroid hormone, and the rest 60μg is returned to the extracellular liquid iodine pool. The organic iodine stored in the thyroid gland in the form of thyroid hormone and iodotyrosine is as high as 8 to 10mg, and the thyroid gland releases 60μg of hormone iodine every day. Iodine intake will affect thyroid hormone secretion.

In other words, the thyroid gland is delicate enough, too high or too low iodine may cause abnormal thyroid function, too low iodine intake will lead to iodine deficiency diseases, and women's iodine deficiency during pregnancy will lead to abortion, premature birth, stillbirth and fetal congenital malformation, which is exactly what salt iodization prevents; Excessive iodine intake may be related to the increase of thyroid diseases, such as hyperthyroidism, hypothyroidism and thyroiditis.